It would be great if there was an aggregate report that sat above the existing reports that listed total sales. It doesn't need to show the breakdown of royalties, just the number of books sold. Having this information at a glance would be really useful when running marketing campaigns in different regions.
I know that other threads have been started for this, so hopefully there is enough demand for this to make it happen.
Other than that - I'm really pleased with KDP. When I used to go via a publisher it would take weeks and weeks for my books to get on Amazon - now it is instant!